Several rechargeable batteries are known. However, they still bear several disadvantages such as high weight, low capacity, slow charging, fast aging etc. In particular for applications with reduced place or intended mobility such as computers, cars and electro bicycles low weight, high capacity, fast charging and long lifetime are desired. During the last years high efforts have been made to improve electrode materials or to reduce the disadvantages mentioned above.
Many materials that gained interest during the last years are ceramic based materials used in nanoparticulate form. These nanoparticles may be polygonal, spherical, or in one direction elongated up to an elongation qualifying them as fibers. One of such fibrous materials is H2V3O8.
H2V3O8 is a known compound that has already been described in 1970 [1] and that was structurally analyzed in 1990 [2]. Also investigated as cathode material was HyNa1-yV3O8 [3]. HyNa1-yV3O8 is described to intercalate up to 3 lithium ions during the first discharging cycle. Upon charging, the three lithium ions are deintercalated.
Although the fibrous H2V3O8 is able to reversibly exchange large amounts (up to 4.5 eq.) of lithium [4], due to the therewith connected volume changes, the fibers decompose into small fragments that show an optimal exchangeability at a certain fragmentation, wherein the capacity is markedly reduced upon further fragmentation so that the stability of the electrode is compromised.
Other cathode materials include Li4V3O8 [5], NaV3O8 [6] and Li1.3-yCuyV3O8 [7], LixFePO4, LixCoO2, LixMn2O4, Lix(MnuCovNiyAlz)O2 with u+v+y+z≈1.
Also suitable anode materials are already known. These include LixC6 and lithium alloys.
Suitable EA materials usually are formed into electrodes by means of a binder that is conductively filled, e.g. with conducting carbon black and/or graphite, and/or that may itself be electronically conducting. The binder and the conducting fillers significantly add to the volume and to the total weight of the battery without actually participating in the charging discharging cycle.
There have already several attempts been made to reduce the weight of the binder/filler matrix, e.g. by using conductive binder in nanoparticulate form (see published European patent application EP 2 228 855) or by preparing a pyrolized product as substitute for a polymeric binder. The disclosure of the above prior publication is incorporated herein in its entirety.
While these attempts brought some weight reduction, there is still a need for a further reduced amount of optionally conductively filled binding material. Said binding material that optionally comprises a conductive filler is further on also referred to as binder matrix or matrix.